Electrolytic Generation of Manganese (III) Ions in Strong Sulfuric Acid

a technology of strong sulfuric acid and electrolysis, which is applied in the production of electrolysis organics, electrolysis components, instruments, etc., can solve the problems of difficult rinsing of chromic acid residues from the polymer surface following treatment, and certain plastic components are suitable for plating

Active Publication Date: 2013-07-25
MACDERMID ACUMEN INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0022]It is still another object of the present invention to provide an im...

Problems solved by technology

However, only certain types of plastic components are suitable for plating.
One problem with the traditional chromic acid etching step is that chromic acid is a recognized carcinogen and is increasingly regulated, requiring that wherever possible, the use of chromic acid is replaced with safer alternatives.
The use of a chromic acid etchant also has well-known and serious drawbacks, including the toxicity of chromium compounds which makes their disposal difficult, chromic acid residues remaining on the polymer surface that inhibit electroless deposition, and the difficulty of rinsing chromic acid residues from the polymer surface following treatment.
Additionally, hot hexavalent chromium sulfuric acid solutions are naturally hazardous to workers.
However, none of these processes have proven satisfactory for various economic, performance and/or environmental reasons and thus none of these processes have achieved commercial success or been accepted by the industry as a suitable replacement for chromic acid et...

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0096]The solution of Comparative Example 1 was electrolyzed by immersing a platinized titanium anode of an area of 1 dm2 and a platinized titanium cathode of surface area 0.01 dm2 in the solution and applying a current of 200 mA for 5 hours.

[0097]During this period of electrolysis, the solution was observed to change in color from almost colorless to a very deep purple / red color. It was confirmed that no permanganate ions were present.

[0098]This solution was then heated to 70° C. and a piece of platable grade ABS was immersed in the solution. After 10 minutes of immersion, the test piece was fully wetted and would support an unbroken film of water after rinsing. After 20 minutes of immersion, the sample was rinsed in water, dried and examined using a scanning electron microscope (SEM). This examination revealed that the test piece was substantially etched and many etch pits were visible.

example 2

[0099]A solution containing 12.5 M of sulfuric acid and 0.08 M manganese(II) sulfate was electrolyzed using a platinized titanium anode at a current density of 0.2 A / dm2. A platinized titanium cathode having an area of less than 1% of the anode area was used in order to prevent cathodic reduction of the Mn(III) ions produced at the anode. The electrolysis was performed for long enough for sufficient coulombs to be passed to oxidize all of the manganese(II) ions to manganese(III). The resulting solution was a deep cherry purple / red color. There were no permanganate ions generated during this step. This was also confirmed by visible spectroscopy—the Mn(III) ions produced a completely different absorption spectrum from that of a solution of permanganate.

example 3

[0100]The etching solution prepared as described above in Example 2 was heated to 65-70° C. on a magnetic stirrer / hotplate and test coupons of ABS were immersed in the solution for time periods of 20 and 30 minutes. Some of these test coupons were examined by SEM and some were processed in a normal plating on plastic pretreatment sequence (reduction in M-neutralize, predip, activate, accelerate, electroless copper plate to 25-30 microns). These test coupons were then annealed and subjected to peel strength testing using an Instron machine.

[0101]Peel strength testing carried out on coupons plated for 30 minutes demonstrated peel strength varying between about 1.5 and 4 N / cm.

[0102]Cyclic voltammograms were obtained from a solution containing 12.5M sulfuric acid and 0.08M manganese sulfate using a platinum rotating disk electrode (RDE) having a surface area of 0.196 cm2 at various rotation speeds. A model 263A potentiostat and a silver / silver chloride reference electrode were used in c...

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Abstract

An electrolytic cell and a method of electrochemical oxidation of manganese(II) ions to manganese(III) ions in the electrolytic cell are described. The electrolytic cell comprises (1) an electrolyte solution of manganese(II) ions in a solution of at least one acid; (2) a cathode immersed in the electrolyte solution; and (3) an anode immersed in the electrolyte solution and spaced apart from the cathode. Various anode materials are described including vitreous carbon, reticulated vitreous carbon, woven carbon fibers, lead and lead alloy. Once the electrolyte is oxidized to form a metastable complex of manganese(III) ions, a platable plastic may be contacted with the metastable complex to etch the platable plastic. In addition, a pretreatment step may also be performed on the platable plastic prior to contacting the platable plastic with the metastable complex to condition the plastic surface.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of application Ser. No. 13 / 677,798, filed on Nov. 15, 2012, now pending, which is a continuation-in-part of application Ser. No. 13 / 356,004, filed on Jan. 23, 2012, now pending, the subject matter of each of which is herein incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates generally to an improved process for etching platable plastics such as ABS and ABS / PC.BACKGROUND OF THE INVENTION[0003]It is well known in the art to plate non-conductive substrates, (i.e. plastics) with metal for a variety of purposes. Plastic moldings are relatively inexpensive to produce and metal plated plastic is used for many applications. For example, metal plated plastics are used for decoration and for the fabrication of electronic devices. An example of a decorative use includes automobile parts such as trim. Examples of electronic uses include printed circuits, wherei...

Claims

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Application Information

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IPC IPC(8): C25C1/10C25C7/00C25B9/17
CPCC25C1/10C25C7/00C25B11/12C09K13/04C25B9/06C25D5/56C25B1/21C25B1/00C25B9/17C25B11/057C25B11/061C25B11/043C25B11/044C09K13/06C25D5/34
Inventor PEARSON, TREVORCLARKE, TERENCECHAPANERI, ROSHAN V.ROBINSON, CRAIGHYSLOP, ALISONSINGH, AMRIK
Owner MACDERMID ACUMEN INC
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